This relates generally to electronic devices and, more particularly, to electronic devices with displays.
Electronic devices often include displays for displaying information to users. The display function in such devices is typically performed by a liquid crystal display (LCD), plasma, or organic light emitting diode (OLED) display element array that is connected to a grid of source (data) and gate (select) metal traces. The display element array is often formed on a transparent panel such as a glass panel, which serves as a protective shield. The data and select lines of the display element array may be driven by a display driver integrated circuit (IC). The driver IC receives an image or video signal, which it then decodes into raster scan pixel values (color or gray scale) and writes them to the display element array during each frame, by driving the data and select lines. This process is repeated at a high enough frame rate so as to render video.
The select lines are sometimes driven using gate driver circuits that are formed directly on the glass panel. Such types of gate driver configuration are sometimes referred to as “gate driver on array” (GOA) technology, which helps to enable a narrower border design for the display. A conventional gate driver typically includes an output transistor that selectively passes through a clock signal. The clock signal is conveyed via a clock routing path that is connected to an entire column of gate drivers. In order to ensure that the amount of capacitive loading on the clock routing path remains below a desired threshold (i.e., to keep power consumption low), the output transistor in each gate driver of the entire column is limited to a certain size.
In high resolution displays with high refresh rates (i.e., refresh rates equal to or greater than 60 Hz) and especially for displays with integrated touch sensing capabilities, it may be challenging to design a gate driver with an output transistor that does not exceed the maximum allowable sizing while meeting performance requirements. It is within this context that the embodiments herein arise.